The present invention relates to a vibration type light-beam chopping apparatus capable of providing an on-off light beam by the use of a vibrating disk which serves as a light-beam interceptor in the path of a light beam. The apparatus finds applications, for example, when used in conjunction with spectrophotometers and optical gas analyzers.
One known light-beam chopping apparatus is of the type wherein a partially cut-away disk rotatively driven by a DC motor is installed between a light source and a light receptor. In this system, however, the use of a motor is indispensable, with the result that the apparatus can hardly be constructed into a small size and also a complicated structure for preventing the leakage of the light beam must be used.
Another prior art light-beam chopping apparatus utilizes an AC exciting coil having an annular shape which is installed in a casing provided with a transparent window or a through-hole for the passage of a light beam. The coil is used as a stator, and a partially cut-away disk having a magnet in its circumferential portion is pivotally mounted on the casing, the magnet being used as a rotor. This system is advantageous in that the size of the apparatus can be reduced, the leakage of the light beam can be prevented, and the construction can be simplified. However, this system requires the use of an AC power source, and the cycle of light which is chopped is variable according to the cycle of the AC power source. To adjust the light chopping cycle, a frequency converter must additionally be used or the construction of the AC coil must be modified each time.
Accordingly, an object of the present invention is to provide a light-beam chopping apparatus which permits the light beam chopping cycle to be readily changed without the need for an AC power source.
Another object of the invention is to provide a light beam chopping apparatus which is simple in construction and driven by a transistor circuit which is operated from a DC battery power source.
A further object of the invention is to provide a light beam chopping apparatus which can be manufactured into a small size at a low cost and is operable with a minimum of light beam leakage.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.